In FIG. 6, a conventional oxygen mask apparatus is shown. A conventional oxygen mask apparatus 81 shown in FIG. 6 differs from an oxygen mask apparatus 1 according to an embodiment of the present invention shown in FIGS. 1 to 5 in points to be described below. That is, in the conventional oxygen mask apparatus 81, a first connector 82 is attached to a mask main body 83 such that the axis of the first connector 82 extends in a substantially vertical direction. In addition, a second connector 84 is formed into a substantially cylindrical shape so that the axis of the second connector 84 extends in a substantially vertical direction. Therefore, oxygen gas which rises substantially vertically from a gas supply tube 85 rises substantially vertically in a third connector 86, and is introduced to the second connector 84. Also, this oxygen gas introduced to the second connector 84 rises in the first connector 82. Accordingly, the oxygen gas rises in the mask main body 83 while diffusing from a relatively large upper-end opening 87 of the first connector 82. Therefore, a mask wearer 91 can relatively easily inhale, from the nostrils, the oxygen gas flowing to an area, below a nose 92, and the surrounding vicinity. Reference numeral 88 denotes three holes in the oxygen mask.
In the conventional oxygen mask apparatus 81, however, the upper-end opening 87 of the first connector 82 has substantially the same diameter as that of an inner circumferential hole (in other words, a through hole) 89 of the first connector 82. Accordingly, the oxygen gas flowing into the mask main body 83 from the upper-end opening 87 may evenly spread to substantially the whole interior of the mask main body 83. To allow the mask wearer 91 to properly inhale the oxygen gas from the nostrils, therefore, a relatively large amount of the oxygen gas must be supplied into the mask main body 83. Accordingly, if the mask main body 83 is not well fitted on a face 93 of the mask wearer 91, the oxygen gas having risen in the mask main body 83 may flow out from the upper end and the surrounding vicinity of the mask main body 83, and flow toward an eye 94 of the mask wearer 91. As a consequence, the eye 94 of the mask wearer 91 may become dry, and the mask wearer 91 may have discomfort on the eye 94.